Patent citations as a measure of knowledge flows:: The influence of examiner citations

Analysis of patent citations is a core methodology-in the study of knowledge diffusion. However, citations made by patent examiners have not been separately reported, adding unknown noise to the data. We leverage a recent change in the reporting of patent data showing citations added by examiners. The magnitude is high: two-thirds of citations on the average patent are inserted by examiners. Furthermore, 40% of all patents have all citations added by examiners. We analyze the distribution of examiner and inventor citations with respect to self-citation, distance, technology overlap, and vintage. Results indicate that inferences about inventor knowledge using pooled citations may suffer from bias or overinflated significance levels.